Stirling refrigerator

ABSTRACT

Provided is a Stirling refrigerator having enhanced cooling capacity through improving exhaust-heat efficiency of the electromagnetic reciprocating drive mechanism. The Stirling refrigerator includes: a casing having a cylindrical portion and a body portion; a cylinder provided with a mount housed within the casing, the mount formed of a metal exhibiting high thermal conductivity; a piston and a displacer housed in the cylinder in a reciprocable manner; a stator of an electromagnetic reciprocating drive mechanism, the stator held on the mount and arranged within the body portion; and a mover of the electromagnetic reciprocating drive mechanism, the mover connected to the piston. The casing is partially formed with a heat-conduction block formed of a metal exhibiting favorable thermal conductivity thermally in contact with the mount. A heat generated at a compression chamber and an electromagnetic reciprocating drive mechanism can be efficiently released to the outside of the casing.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims a priority to Japanese Patent Application No. 2015-036985, filed Feb. 26, 2015, the entirety of which is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a Stirling refrigerator, particularly to a free-piston type Stirling refrigerator in which an electromagnetic reciprocating drive mechanism and a compression chamber are positioned comparatively close to each other.

BACKGROUND

Conventionally, as a Stirling refrigerator of such type, there has been disclosed a Stirling refrigerator in e.g., Japanese Patent No. 3769751, provided with:

a casing having a cylindrical portion;

a cylinder inserted into the casing;

a displacer and a piston that are inserted into the inside of the cylinder;

a driving unit for reciprocating the piston; and

a mount provided on an outer circumference of the cylinder,

wherein supported on the mount is a stator of the driving unit comprising a laminated core and an electromagnetic coil.

When an alternating current is applied to the electromagnetic coil to reciprocate the piston within the cylinder, the displacer starts reciprocating with a predetermined phase difference relative to the piston. On this occasion, the compression chamber, provided between the piston and the displacer, is brought into a high temperature state while the expansion chamber, located on the other side of the compression chamber across the displacer, is brought into a low-temperature state. By utilizing such phenomenon that the surroundings of this expansion chamber are brought into a low temperature state, the refrigerator is thus capable of cooling a cooling target. On the other hand, as a heat is generated in the compression chamber, it needs to be cooled.

Casings for such Stirling refrigerators are generally formed of a comparatively thick stainless steel material. One of the reasons for employing such material is because it is necessary to make a leakage of helium less likely to occur since helium is often used as an operating gas encapsulated in the casing of such Stirling refrigerator and helium is the nearest to the ideal gas and prone to be leaked. Other reasons therefor are because the casing needs to be manufactured from a metal capable of withstanding a high pressure as an operating gas is encapsulated therein at a high pressure; and stainless steel is relatively inexpensive and has an excellent workability and corrosion resistance.

Such Stirling refrigerators, however, generate heat not only in a compression chamber but also in an electromagnetic reciprocating drive mechanism. The heat generated in the electromagnetic reciprocating drive mechanism originates from Joule heat (or copper loss) caused by an electric current flowing through the electromagnetic coil, as well as a loss at a laminated core (or iron loss). Then, if you attempt to enhance the cooling capacity of such Stirling refrigerators, you need to supply an increased amount of an electric power to the electromagnetic reciprocating drive mechanism, resulting in an increased amount of heat being generated at the electromagnetic reciprocating drive mechanism. Obviously, such heat must be eliminated. As described above, however, the casing is generally formed of a stainless steel material not so high in thermal conductivity. For this reason, and along with the material being comparatively thick, there have been concerns about the electromagnetic reciprocating drive mechanism being unable to be cooled down to the full extent. This problem has been a main factor hindering the improvement of the cooling capacity of Stirling refrigerators.

SUMMARY

It is, therefore, an object of the present invention to solve the above-mentioned problems and provide a Stirling refrigerator having an enhanced cooling capacity by improving exhaust-heat efficiency of the electromagnetic reciprocating drive mechanism.

A first aspect of the present invention is a Stirling refrigerator including:

a casing having a cylindrical portion and a body portion;

a cylinder provided with a mount housed within the casing, the mount formed of a metal exhibiting high thermal conductivity;

a piston and a displacer that are housed in the cylinder in a reciprocable manner;

a stator of an electromagnetic reciprocating drive mechanism, the stator held on the mount and arranged within the body portion; and

a mover of the electromagnetic reciprocating drive mechanism, the mover connected to the piston,

wherein the casing is partially formed with a heat-conduction block formed of a metal exhibiting high thermal conductivity, and the heat-conduction block is thermally in contact with the mount.

A second aspect of the present invention is a Stirling refrigerator as set forth in the first aspect wherein the heat-conduction block is provided on the outside of the compression chamber defined between the piston and the displacer.

Further, a third aspect of the present invention is a Stirling refrigerator as set forth in the second aspect wherein on the body portion is formed at least one through-hole through which a heat pipe or thermosiphon is inserted into the body portion, and a gap provided between the through-hole and the heat pipe or thermosiphon is sealed.

According to the first aspect of the present invention and by virtue of the above-described configuration of the Stirling refrigerator, a heat generated at the stator of the electromagnetic reciprocating drive mechanism is allowed to be released to the outside of the casing through the mount and the heat-conduction block 4 that are formed of a metal having a high thermal conductivity. Thus, the electromagnetic reciprocating drive mechanism can be fully cooled, thus enhancing the cooling capacity of the Stirling refrigerator.

Further, the heat-conduction block is provided on the outside of the compression chamber defined between the piston and the displacer, whereby a heat generated in the compression chamber can also be released through the heat-conduction block at the same time.

Furthermore, on the body portion is formed at least one through-hole through which a heat pipe or a thermosiphon is inserted into the body portion, while a gap between the through-hole and the heat pipe (or thermosiphon) is sealed.

By virtue of this configuration, when the temperature in the compression chamber is higher than that of the stator, there can be released a heat, transferred from the compression chamber through the heat-conduction block and the mount into the body portion, to the outside of the casing by using the heat pipe or thermosiphon.

On the other hand, when the temperature in the compression chamber is lower than that of the stator, there can be released a heat, transferred from the stator through the mount to the heat-conduction block, to the outside of the casing through the heat-conduction block.

Therefore, irrespective of which one of the compression chamber and the stator has a higher temperature than the other, heats generated all across the Stirling refrigerator can be fully released.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view showing a Stirling refrigerator of a first example of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main section of the Stirling refrigerator shown in FIG. 1.

DETAILED DESCRIPTION

Examples of the present invention will now be described hereunder with reference to the accompanying FIGS. 1 and 2. The following examples shall not limit the contents of the present invention that are described in the claims. Further, not all elements described hereunder are necessarily the essential elements of the present invention. For convenience of description, it is to be noted that when referring to the terms “upper” and “lower” of the Stirling refrigerator, these terms are respectively defined as upper and lower of the drawings.

Example

As shown in FIG. 1, numeral 1 denotes a casing forming an outer hull of the Stirling refrigerator. The casing 1 includes: a cylindrical portion 2 and a body portion 3 that have a substantially cylindrical shape; a heat-conduction block 4 having a substantially cylindrical shape with a lower end thereof formed into a flange shape; and an annular block 5 having an annular plate shape.

The cylindrical portion 2 is integrally formed with a main body 2A and a distal portion 2B, and is open at a lower end thereof. The cylindrical portion 2 is formed entirely of a metal such as stainless steel.

The body portion 3 has a substantially U-shaped, bottomed cylindrical shape when viewed in a longitudinal section, and is open at an upper end thereof. On a main body portion 3A are formed a plurality of through-holes 3B for inserting later-described heat pipes 36 thereinto. The body portion 3 is formed entirely of a metal such as stainless steel.

Next, the heat-conduction block 4 and the annular block 5 are described with reference to FIG. 2. The heat-conduction block 4 is integrally formed of: a block body 4A having a substantially cylindrical shape whose top and bottom are open; and a flange portion 4B extended horizontally in an outer circumferential direction from a lower end of the block body 4A. An inner circumference of the lower end of the block body 4A is formed with a chamfer 4C. Also, an outer circumference of the flange portion 4B is formed with a vertically two-step structure in which a lower step 4E is protruded outwardly of an upper step 4D toward an outer circumferential direction. The heat-conduction block 4 is formed of a metal, such as copper, exhibiting a higher thermal conductivity and strength as compared to a metal such as stainless steel constituting the body portion 3.

The annular block 5 has a substantially annular plate shape in a planar view. An inner circumference of the annular block 5 is formed with upper and lower two steps in which an upper step 5A is protruded inwardly of a lower step 5B in an inner circumferential direction. These upper and lower steps 5A, 5B are respectively abutted on and joined to the upper and lower steps 4D, 4E through brazing. An outer circumference 5C of the annular block 5 is welded to an inner surface of the body portion 3. The annular block 5 is formed entirely of stainless steel. Alternatively, the welded portion of the heat-conduction block 4 and the annular block 5 may be formed into another shape.

An upper end surface 3C of the body portion 3, an upper surface 5D of the annular block 5 and upper surface 4F of the flange portion 4B are flush with each other. Further, a lower surface 5E of the annular block 5 and a lower surface 4G of the flange portion 4B are flush with each other. Furthermore, a lower end portion of the cylindrical portion 2 is joined to an inner circumference of an upper end portion of the heat-conduction block 4 through brazing.

A cylinder 7 extending up to the inside of the body portion 3 is coaxially inserted into the cylindrical portion 2. An extended cylinder portion 6, separate from the cylinder 7, is coaxially connected to a cylinder distal portion 7A. The cylinder 7 is integrally formed with later-described mounts 26, 27 and connecting arms 30 by casting, such as die casting or the like, using a metal such as aluminum, followed by subjecting inner and outer peripheral surfaces, etc. of the cylinder 7 to cutting work after casting.

A displacer 8 is slidably provided within the cylinder distal portion 7A and the extended cylinder portion 6 in the axial direction. Also, an expansion chamber E is provided between a distal end portion 8A of the displacer 8 and the distal portion 2B of the cylindrical portion 2. Inside and outside of the extended cylinder portion 6 are communicated with each other via a space 9.

Also, a regenerator 10 is provided between the inner circumference of the main body 2A of the cylindrical portion 2 and the outer circumference of the extended cylinder portion 6. Further, on the cylinder 7 is formed a communication hole 11 for allowing the inside of the cylinder 7 to communicate with the outside thereof.

A heat absorbing fin 12 is provided between the inner circumference of the distal portion 2B and the outer circumference of the distal end of the extended cylinder portion 6, while a heat dissipating fin 13 is provided between the outer circumference of the cylinder 7 and the inner circumference of the cylindrical portion 2, in a position between the regenerator 10 and the communication hole 11. Then, there is formed a path 14 extending from the inside of the distal end of the extended cylinder portion 6 up to the compression chamber C within the cylinder 7 through the space 9, the heat absorbing fin 12, the regenerator 10, the heat dissipating fin 13 and the communication hole 11.

Further, a piston 15 is provided on the inside of the cylinder base portion 7B of the cylinder 7 within the body portion 3 in a manner capable of sliding therein in the axial direction.

An electromagnetic reciprocating drive mechanism 16 that serves as a driving mechanism for reciprocating the piston 15 includes:

a mover 17 of a short cylindrical shape, provided on the outside of the cylinder base portion 7B in a manner extending coaxially therewith;

a cylindrical permanent magnet 18 fixed to one end of the mover 17;

a ring-shaped electromagnetic coil 19 provided adjacent to the outer circumference of the permanent magnet 18; and

a magnetism inductor portion 20 provided adjacent to the inner circumference of the permanent magnet 18. The electromagnetic coil 19 is wound around a stator 24, while the stator 24 is integrated with the electromagnetic coil 19.

A lower part 15A of the piston 15 located at a lower end part of the piston 15 is connected to a bottom part 17A of the mover 17 located at a bottom thereof. The piston 15 and the mover 17 are structured so as to work with each other. Here, the lower part 15A of the piston 15 is connected to a first flat spring 21 for controlling a movement of the piston 15. Further, to a lower end of the aforementioned displacer 8 is connected one end of a rod 22 for controlling the movement of the displacer 8, and the other end of the rod 22 is connected to a second flat spring 23. This rod 22 extends in a manner penetrating through the piston 15. As for a pair of the first flat spring 21 and the second flat spring 23, they are provided below the cylinder 7 within the body portion 3, with the second flat spring 23 being positioned lower than the first flat springs 21.

Between the cylinder distal portion 7A and the cylinder base portion 7B is integrally formed the aforesaid mount 26 in a manner coaxial therewith. At a lower end of the mount 26 is integrally formed the aforesaid mount 27 of a flange type extending in an outer circumferential direction.

There is formed a fine gap between the outer periphery of the mount 26 and the inner periphery of the heat-conduction block 4. Further, on the outer periphery of the mount 26 is formed a tapered portion 26A having a tapered shape corresponding to the chamfer 4C formed on the heat-conduction block 4. Furthermore, on the outer periphery of the mount 26 is formed a concave groove 26B on which an O-ring 25 is mounted. The fine gap provided between the mount 26 and the heat-conduction block 4 is sealed by this O-ring 25.

An upper surface 27A of the mount 27 is formed into a flat shape so as to be thermally in contact or abutted with a lower surface 4G of the flange portion 4B of the heat-conduction block 4. Further, a lower surface 27B of the mount 27 is formed so as to be abutted with an upper surface of the stator 24 constituting the electromagnetic reciprocating drive mechanism 16. Furthermore, on the lower surface of the stator 24 is abutted a fixation ring 28, thus sandwiching the stator 24 between the fixation ring 28 and the mount 27. This way, the stator 24, and eventually the electromagnetic coil 19 that is integrated with the stator 24, are fixed to the mount 27.

From a lower surface of the outer circumferential portion of the mount 27, a plurality of the connecting arms 30 extend downwardly in a direction substantially parallel with an axial direction of the cylinder 7. Note that the plurality of connecting arms 30 are integrally formed with the mount 27.

Distal end surfaces 30B of the connecting arms 30 are formed on the same plane in a manner orthogonally crossing the axial direction of the cylinder 7. On each of the distal end surfaces 30B is formed a screw hole 30C having an internal thread in parallel with the axial direction of the cylinder 7. The aforesaid first flat spring 21 contacts the distal end surfaces 30B. The first flat spring 21 is sandwiched and supported between the connecting arms 30 and respective spacers 31 while being in contact with the distal end surfaces 30B. Meanwhile, each spacer 31 employs such a structure that its main body 31A has a regular hexagonal pillar shape; one end thereof has a male screw 31B formed coaxially with the main body 31A so as to be screwed into the internal thread 30C; the other end surface 31C thereof has a screw hole 31D having an internal thread formed coaxially with the main body 31A. Then, by screwing the male screws 31B provided at one end of the spacers 31 into the respective screw holes 30C of the connecting arms 30 via the screw holes 21A formed in the first flat spring 21, the first flat spring 21 is sandwiched between the connecting arms 30 and the spacers 31. At this moment, since the spacers 31 have a regular hexagonal pillar contour, it is easy to attach the spacers 31 to the respective connecting arms 30 by tightening with a wrench or the like.

With the spacers 31 being attached to the respective connecting arms 30, the spacers 31 are formed flush with each other such that the other end surfaces 31C thereof orthogonally intersect with the axis of the cylinder 7, and the second flat spring 23 comes in contact with the other end surfaces 31C. With the second flat spring 23 being in contact with the other end surfaces 31C, it is fixed to the spacer 31 by fitting the screws 32 into the internal thread of the screw holes 31D via the screw holes 23A formed in the second flat spring 23

Outside the connecting arms 30 are provided a plurality of the heat pipes 36 having a substantially L-shape. Each of these heat pipes 36 has a structure integrally formed with: a basal portion 36A arranged within the body portion 3 in parallel with an axial direction of the piston 15; and an arm portion 36B protruded in parallel through the through-holes 3B formed on the main body portion 3A toward the outside of the body portion 3, or of the casing 1. Between the heat pipe 36 and the through-hole 3B is provided a gap 37, which is sealed by a brazing joint 38.

The heat pipes 36 are well known in the art, yet just to make sure, they will be described herein below. The heat pipes 36 are made of pipes formed of a metal such as copper having high thermal conductivity. The pipes are evacuated inside and an operating fluid is encapsulated therein. On the inner wall of the heat pipes 36 are formed wicks, or capillary structures (not shown). The basal portions 36A are arranged in a position opposed to the electromagnetic coil 19 and function as heat receiving portions for receiving a heat generated, due to the current flow, from the electromagnetic coil 19. Meanwhile, the arm portions 36B function as heat dissipating portions for releasing a heat received at the basal portions 36A to the outside of the casing 1 in which the temperature outside of the casing 1 is lower than the temperature within the casing 1.

The basal portions 36A will be heated by a heat generated from the electromagnetic coil 19, and then the operating fluid inside the basal portions 36A will be evaporated. The evaporated operating fluid will be then transferred to the arm portions 36B of a lower temperature, and will be cooled, condensed and liquefied there. On the inner wall of the heat pipes 36 are formed wicks, which will bring the operating fluid liquefied at the arm portions 36B back to the basal portions 36A by so called capillary action. In this case, since the liquefied operating fluid is transported through the capillary action, the liquefied operating fluid is allowed to be refluxed from the arm portions 36B to the basal portions 36A, irrespective of the posture of the heat pipes 36, or that of the Stirling refrigerator provided with the heat pipes 36. In this way, the heat pipes 36 have a high thermal conductivity through circulating an operation fluid.

In this way, since the heat pipes 36 have a high thermal conductivity through circulating an operation fluid, a heat generated at the electromagnetic coil 19 can be efficiently released to the outside of the casing 1. Note that, although in the figures, the heat pipes 36 and the connecting arms 30 are arranged adjacent to each other, each of the heat pipes 36 is preferably to be arranged in between the plurality of connecting arms 30 in practical use. Also note that the heat pipes 36 are capable of releasing to the outside of the casing 1 not only the heats generated at the electromagnetic reciprocating drive mechanism 16 but also the heats of the operating fluid inside the body portion 3 heated by the heat generated in the electromagnetic reciprocating drive mechanism 16 and/or the compression chamber C.

Alternatively, there may be employed a thermosiphon (not shown) in place of the heat pipe 36. Such thermosiphons are also well known in the art, yet just to make sure, they will be described herein below. The thermosiphons are made of pipes formed of a high thermal conductive metal such as copper. The pipes are evacuated inside and an operating fluid is encapsulated therein. Also, on the upper and lower portion of the thermosiphon are respectively provided a heat receiving portion and a heat dissipating portion. The operating fluid encapsulated therein will be heated at the heat receiving portion and then vaporized to move upward through the thermosiphons. The vaporized operating fluid will then be cooled, condensed and liquefied at the heat dissipating portion. The liquefied operating fluid will move downward by gravity through the thermosiphons to be refluxed back to the heat receiving portion. As for such thermosiphon, there may be employed a single pipe thermosiphon of a type having no wick structure (or no capillary structure), or a so-called looped thermosiphon provided with: a pipe through which the vaporized operating fluid travels upwardly; and a pipe through which the liquefied operating fluid moves downwardly.

A numeral 33 denotes a vibration absorbing unit 33 provided at a lower part of the casing 1, in which a plurality of flat springs 34 and a balance weight 35 are coaxially arranged such that the flat springs 34 are stacked on the balance weight 35 through coupling members arranged on the axial line of the cylinder 7. This vibration absorbing unit 33 serves to absorb vibration of the casing caused by the reciprocating movements of the piston 15 and the displacer 8.

Next is an explanation of the action of the present example. First, an alternating current of a predetermined frequency will be applied to the electromagnetic coil 19 of the stator 24 of the electromagnetic mechanism 16 from a power source (not shown) provided outside the casing 1 via a driving circuit (not shown) and a power cord. By applying an alternating current to the electromagnetic coil 19 this way, an alternating magnetic field will be generated from the electromagnetic coil 19 and be concentrated around the stator 24. Then, this alternating magnetic field generates a force to reciprocate the mover 17 along the axial direction thereof. Due to this force, the piston 15, connected to the mover 17 to which the permanent magnet 18 is fixed, will start reciprocating in the cylinder 7 along the axial direction thereof.

When the piston 15 comes closer to the displacer 8, a gas, which is in the compression chamber C provided between the piston 15 and the displacer 8, is compressed and flows into the expansion chamber E provided between a distal end of the displacer 8 and the distal portion 2B of the cylindrical portion 2, through the communication hole 11, the heat dissipating fin 13, the regenerator 10, the heat absorbing fin 12 and the space 9. Consequently, the displacer 8 is pushed downwardly with a predetermined phase difference relative to the piston.

On the other hand, when the piston 15 moves away from the displacer 8, the inside of the compression chamber C is subjected to negative pressure, and the gas in the expansion chamber E flows back from the expansion chamber E to the compression chamber C through the space 9, the heat absorbing fin 12, the regenerator 10, the heat dissipating fin 13 and the communication hole 11. Accordingly, the displacer 8 is pressed upwardly with the predetermined phase difference relative to the piston 15.

Throughout these processes, a reversible cycle, consisting of two changes of an isothermal change and an isochoric change, will be carried out. Consequently, a part adjacent to the expansion chamber E is brought into a low-temperature state and a part adjacent to the compression chamber C is brought into a high-temperature state. Moreover, since the heat-conduction block 4 is provided outside of the compression chamber C so as to encircle the compression chamber C, there can be received a compression heat of a gas compressed within the compression chamber C in a direct and efficient manner.

Moreover, the heat-conduction block 4 is in contact with the heat dissipating fin 13 and the mount 27. For this reason, there can be also received a heat conducted from the compression chamber C to the heat dissipating fin 13 and/or the mount 27 in an efficient manner. Further, the heat-conduction block 4 is allowed to receive a heat conducted from the electromagnetic reciprocating drive mechanism 16 to the mount 27 in an efficient manner. The heat-conduction block 4 serves to release heats, received from above mentioned parts, to the outside of the casing 1 having lower temperature. In this way, cooling capacity of the Stirling refrigerator can be enhanced.

In the meantime, when a more electric power is supplied to the electromagnetic coil 19 to enhance the cooling capacity of the Stirling refrigerator, there is generated an increased amount of heat at the electromagnetic reciprocating drive mechanism 16 and the compression chamber C. Nevertheless, such heat can be fully released through the heat-conduction block 4 and the heat pipes 36 even when an increased amount of heat is generated at the electromagnetic reciprocating drive mechanism 16 and the compression chamber C. When an amount of heat generated at the electromagnetic reciprocating drive mechanism 16 is greater than that generated at the compression chamber C, the heat generated at the electromagnetic reciprocating drive mechanism 16 is allowed to be released or dissipated through the heat pipes 36 as well as through this heat-conduction block 4 after the heat conducts from the mount 27 to the heat-conduction block 4. On the other hand, the heat generated at the compression chamber C is to be released out through the heat-conduction block 4.

In contrast, when an amount of heat generated at the electromagnetic reciprocating drive mechanism 16 is smaller than that generated at the compression chamber C, the heat generated at the electromagnetic reciprocating drive mechanism 16 is allowed to be released out through the heat pipes 36, while the heat generated at the compression chamber C is allowed to be released out through the heat-conduction block 4 as well as through the heat pipes 36 after the heat conducts from the heat-conduction block 4 through the mount 27 to the heat pipes 36 provided in the vicinity of this mount 27.

That is, irrespective of which one of the compression chamber C and the stator 24 of the electromagnetic reciprocating drive mechanism 16 has a higher temperature than the other, heats generated all across the Stirling refrigerator can be satisfactorily released.

As described above, the Stirling refrigerator of the present example includes:

a casing 1 having a cylindrical portion 2 and a body portion 3;

a cylinder provided with a mount 27 housed within the casing 1, the mount 27 formed of a metal exhibiting high thermal conductivity;

a piston 15 and a displacer 8 housed in the cylinder 7 in a reciprocable manner;

a stator of an electromagnetic reciprocating drive mechanism 16, the stator held on the mount 27 and arranged within the body portion 3; and

a mover of the electromagnetic reciprocating drive mechanism 16, the mover connected to the piston 15; wherein

the casing 1 is partially formed with a heat-conduction block 4 formed of a metal exhibiting favorable thermal conductivity and the heat-conduction block 4 is thermally in contact with the mount 27.

By virtue of this configuration, a heat generated at the stator 24 for the electromagnetic reciprocating drive mechanism 16 can be released out through the mount 27 and the heat-conduction block 4 that are formed of a metal having favorable thermal conductivity to the outside of the casing 1. For this reason, the electromagnetic reciprocating drive mechanism 16 can be fully cooled. Consequently, cooling capacity of the Stirling refrigerator can be enhanced.

Further, since there is provided the heat-conduction block 4 on the outside of the compression chamber C defined between the piston 15 and the displacer, a heat generated at the compression chamber C can be released through the heat-conduction block 4. By virtue of this configuration, cooling capacity of the Stirling refrigerator can be enhanced.

Furthermore, on the body portion 3 is formed through-holes 3B through which heat pipes 36 or thermosiphons are inserted into the body portion 3. Gaps 37 provided between the through-holes 3B and the heat pipes 36 (or thermosiphons) are sealed. By virtue of this configuration, when the temperature in the compression chamber C is higher than that of the stator 24, there can be released a heat, transferred from the compression chamber C through the heat-conduction block 4 and the mount 27 to the body portion, to the outside of the casing 1 by using the heat pipes 36 or thermosiphons.

On the other hand, when the temperature in the compression chamber C is lower than that of the stator 24, there can be released a heat, transferred from the stator 24 through the mount 27 to the heat-conduction block 4, to the outside of the casing 1 through the heat-conduction block 4. Therefore, irrespective of which one of the compression chamber C and the stator 24 has a higher temperature than the other, heats generated all across the Stirling refrigerator can be fully released.

The present invention shall not limited to the example described above and various modifications are possible within the scope of the gist of the present invention. For example, although tubular shaped heat pipes are employed in the foregoing example, there may be employed a heat pipe of any other shape, such as a sheet-shaped heat pipe. 

What is claimed:
 1. A Stirling refrigerator comprising: a casing having a cylindrical portion and a body portion; a cylinder that is housed within said casing and provided with a mount formed of a metal exhibiting a high thermal conductivity; a piston and a displacer that are housed in said cylinder in a reciprocable manner; and an electromagnetic reciprocating drive mechanism having a stator and a mover, said stator being held on said mount and arranged within said body portion, while said mover being connected to said piston, wherein said casing is partially formed with a heat-conduction block formed of a metal exhibiting a high thermal conductivity, and said heat-conduction block is thermally in contact with said mount.
 2. The Stirling refrigerator according to claim 1, wherein said heat-conduction block is provided on an outside of a compression chamber defined between said piston and said displacer.
 3. The Stirling refrigerator according to claim 2, further comprising at least one through-hole formed on said body portion, wherein a heat pipe or a thermosiphon is inserted through said through-hole into said body portion, and a gap defined between said through-hole and said heat pipe or said thermosiphon is sealed.
 4. The Stirling refrigerator according to claim 1, further comprising a compression chamber defined between said piston and said displacer in a manner being surrounded by said mount.
 5. The Stirling refrigerator according to claim 4, wherein said heat-conduction block is provided on an outside of said compression chamber.
 6. The Stirling refrigerator according to claim 3, wherein said heat pipe or said thermosiphon comprises: a basal portion arranged in parallel with an axial direction of said piston; and an arm portion protruded horizontally toward an outside of said casing.
 7. The Stirling refrigerator according to claim 6, wherein said basal portion is arranged in a position opposed to said electromagnetic reciprocating drive mechanism.
 8. The Stirling refrigerator according to claim 3, further comprising a plurality of connecting arms at a lower surface of an outer circumference of said mount, said connecting arms protruding downwardly in a direction substantially parallel with an axial direction of said cylinder.
 9. The Stirling refrigerator according to claim 8, wherein said heat pipe or said thermosiphon is arranged in between the plurality of connecting arms.
 10. The Stirling refrigerator according to claim 8, wherein said heat pipe or said thermosiphon is arranged adjacent to each of the plurality of connecting arms.
 11. The Stirling refrigerator according to claim 1, further comprising a heat dissipating fin in contact with said heat-conduction block, wherein said compression chamber is in communication with said heat dissipating fin. 